On 3/13/2011 3:17 PM, Tim Johnson wrote:
* Tim Johnson<t...@johnsons-web.com> [110313 08:27]:
One other thing I just realized:
The process stops inside of a function call to another object
method, if that method call is removed, the process teminates.
:) I may have a solution later today, and will relay it to you if
found. Must have coffee first.
I've had coffee, and also I've eaten a bit of crow. If I had no
dignity to spare I might have dropped this thread after the last
post, but I owe it to those who might come after me to explain
what happened. If I have any excuse, it is that I wrote this code
when I had about a month of python experience.
One measure of people is how big a mistake they are willing to make --
in public. I learned to always test or disclaim as 'not tested' posted
code by posting undisclaimed bad code -- more than once.
So here we go...
The cleanup part is to write a logfile. The logfile is written by
the write() method of a log object. The method was coded to accept
any number of data types and execute based on the type from an
if/elif/else code block. The cgi object was passed to the method.
The original code follows:
## code begins
if type(args) == type({}): ## it's a dictionary
args['time_date_stamp'] = '%s%d' %
(std.local_time(),std.randomize(8))
keys = args.keys()
keys.sort()
for key in keys:
outfile.write('\t%s: %s\n' % (key,args[key]))
elif type(args) == type(''):
outfile.write('%s\n%s\n' % (std.local_time(),args))
elif std.IsCgiObj(args): ## dump the cgi object
dump = args.getEnv('time_date_stamp=%s' %
(std.local_time()))
for line in dump:
outfile.write(' %s\n' % line)
else : ## default = it's a list
if args:
outfile.write('time_date_stamp=%s\n' %
(std.local_time()))
for arg in args:
outfile.write(' %s\n' % arg)
## /code ends
I did two obvious things wrong here:
First of all, std.IsCgiObj() returned false when I changed
the class name because std.IsCgiObj() tested for an explicit
match of 'cgitools' with the objects __class__.__name__ member.
Your fundamental problem is that you changed the api of your module.
When you do that, you have to review all code that uses that api -- or
that depends on it. But yes, a module can use a string based on the api
without actually importing the module. Bad idea I think. Better to
import the module and make the dependency overt, so the failure is also.
The test should be (and should have been)
elif isinstance(args, cgi.cgitools):
This would have and will fail with a loud AttributeError when cgitools
is renamed.
Secondly, and worse, the default of the test block was an assumption
and I did not test the assumption. Bad, bad, very bad!
Therefore my code attempted to process the object as a list and down
the Rabit Hole we went. And I ended up with some *really* big
logfiles :).
Thank you for confirming that I was basically right that *somewhere*
there had to be a test for the name 'cgitools' whose failure lead to a loop.
Following is a tentative revision:
## code begins
elif 'instance' in (str(type(args))): ## it's an object
*Everything* is an object and therefore an instance of some class. What
you are testing is whether the object is an instance of a classic class
defined by a Python 2.x (classic) class statement. Rather fragile;-), as
I just hinted.
class C(): pass
C()
# 2.7 prints
<__main__.C instance at 0x00C41FD0>
# 3.2 prints
<__main__.C object at 0x00F0A5F0>
class C(object): pass
C()
# 2.7 also prints
<__main__.C object at 0x00C71130>
if hasattr(args,'getEnv'): ## test for method
dump = args.getEnv('time_date_stamp=%s' %
(std.local_time()))
for line in dump:
outfile.write(' %s\n' % line)
else :
erh.Report("object passed to logger.write() must
have a `getEnv()' method" )
else : ## it's a list
just test elif isinstance(args, list): ...
and put error message in separate else; clause
if type(args) != []: ## make no assumptions
erh.Report('List expected in default condition
of logger.write()')
if args:
outfile.write('time_date_stamp=%s\n' %
(std.local_time()))
for arg in args:
outfile.write(' %s\n' % arg)
## /code ends
> ## erh.Report() writes a messages and aborts process.
Consider upgrading to 2.7 if you have not and using the logging module.
Of course, I could have problems with an object with a
malfunctioning getEnv() method, so I'll have to chew that one over
for a while.
I appreciate Terry's help. I'd welcome any other comments. I'm
also researching the use of __class__.__name__. One of my questions
is: can the implementation of an internal like __class__.__name__
change in the future?
Double double underscore names are 'special' rather than necessarily
'private'. These two are somewhat documented (3.2 Reference, 3.1,
"__class__ is the instance’s class", "__name__ is the class name"). So
they will not change or disappear without notice. I expect them to be
pretty stable.
On the other hand, they are mostly intended for internal use by type(ob)
(for every ob), str/repr(ob) (for many obs), tracebacks, and other
messages. Indeed, one 'should' use type(ob) rather than ob.__class__.
However, custom messages may require direct use of .__name__. As you
discovered, using it for program logic has problems.
--
Terry Jan Reedy
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